The present invention is generally related to the field of line driver devices, and more particularly to an apparatus and method for reducing the overhead power dissipation of an ADSL line driver amplifier.
Generally, line drivers used in Central Office (CO) operating Asymmetrical Digital Subscriber Line (ADSL) applications have been known to dissipate too much power. Although progress has been made in the last several years in reducing line driver power dissipation, the demand for increased circuit density in a fixed space with fixed thermal cooling capabilities requires that line driver power dissipation be decreased even further.
Conventional line driver amplifiers are typically Class G topology amplifiers which linearly and continuously transition between the upper and lower power supplies of the amplifier. These power supply voltages typically use varying amounts of current from both supplies depending on the amplitude of the signal being amplified. However, this requires the amplifier to generate an overhead voltage in its output stage so as to prevent distortion in the amplified signal. This overhead voltage significantly increases the power dissipation of the device.
Accordingly, there is needed a line driver device having reduced power dissipation that allows for higher density packaging of ADSL circuits.
The present invention achieves technical advantages as a line driver circuit that takes advantage of the xe2x80x9cpeakyxe2x80x9d nature of an ADSL signal by running a line driver amplifier from a lower set of power supply voltages as a baseline, and from a higher set of voltages only when the amplitude of the signal being transmitted requires it. Advantageously, this reduces the power dissipation in the line driver by operating the line driver the majority of the time from the lower supply voltage.
In one embodiment, the invention is an ADSL line driver circuit with reduced power consumption capabilities. The line driver circuit includes an amplifier amplifying the input signal. Preferably, a switching circuit is adapted to selectively establish which power supply voltages are driving the line amplifier. This switching is initiated in response to detecting the voltage amplitude of the input signal reaching a predetermined threshold level.
In another embodiment, the invention is a method for reducing the power consumption of an ADSL line driver circuit, where the method includes the steps of receiving a input signal having a voltage amplitude, and amplifying the input signal using an amplifier in response to the detected amplitude of the input signal. The amplifier is discretely powered by a selected power supply voltage. Advantageously, the line driver amplifier is discretely switched between an upper and lower set of supply voltages in order to draw required current from either the upper or lower power supplies as a function of the input signal amplitude. A delay circuit issued to allow the switching of power supplies driving the amplifier.